I messed up any advice appreciated
I bought a 2016 Altima 3.5 with 151k miles from a buy here pay here with a misfire, I thought it would be something easy to fix like plugs and coils and it would be good to go but I was wrong, after trying literally everything to get this engine running right I finally did a compression test on cylinder 4 the one that is misfiring and got 60psi compared to the others reading at 150psi, I removed the valve cover and was met with a bunch of sludge, ran seafoam through the oil and tried to clear it out and done an oil change 200 miles later, the misfire is still there and I have no clue what to look for next I’m kinda new to all of this and don’t really know what to try next I owe 8k on this car and don’t have any type of warranty, I fear I’m gonna have to replace the whole engine and I’m regretting it big time I’m only 22 and this is only the second car I’ve ever bought I wish I would’ve looked around more before buying